Photoflash lamp

ABSTRACT

A photoflash lamp of the combustible type, wherein an ignition mass is provided in a cavity of an insulating member, with the ends of the current conductors ending in said cavity that diverges outward toward the end of the bulb remote from the base, the oxidizable metal present in the lamp being kept at a suitable distance from said ends.

United States Patent Inventors Johannes Cornell's Van der Tas;

Charles Cornelis Eduard Meulemans; Karlo Pedro Martens, all 01 Emmasingel, Eindhoveu, Netherlands Sept. 24, 1969 Aug. 31, 1971 U.S. Philips Corporation New York, N.Y.

Sept. 27, 1968 Netherlands App]. No. Filed Patented Assignee Priority PHOTOFLASH LAMP 7 Claims, 5 Drawing Figs.

US. Cl

431/95 F2lk 5/02 Field 01 Search .I. 431/93, 94, 95

References Cited UNITED STATES PATENTS 2,305,561 12/1942 Sylvester 431/95 2,361,495 10/1944 Pipkin 431/95 2,768,517 10/1956 Atkinson 431/95 2,771,765 10/1956 Arnott et a1. 431/95 2,972,937 2/1961 Suits 431/93 UX 3,224,236 12/1965 DeMent 431/94 UX Primary Examiner-Edward .1. Michael Attorney-F rank R. Trifari ABSTRACT: A photoflash lamp 'of the combustible type, wherein an ignition mass is provided in a cavity of an insulating member, with the ends of the current conductors ending in said cavity that diverges outward toward the end of the bulb remote from the base, the oxidizable metal present in the lamp being kept at a suitable distance from said ends.

mammal IBYI SHEET 1 0F 2 INVENTORS MN DER 7A5 MEULEMAN MARTENS Jomubes c. CHARLES 0.5.

KARLO P PATENIED meal l9" SHEU 2 BF 2 INVENTORS JOHANES C. VAN DER TAS CHARLES cs. MEULEMANS KARLO E MARTENS M Mal-1m PHOTOFLASH LAMP The invention relates to a photoflash lamp of the combustible type comprising an envelope of a light-pervious material containing an oxidizable metal and an oxidizing gas, which lamp comprises an electric ignition mechanism which is provided with two current conductors which can be connected to a voltage source outside the lamp and which are fixed relative to each other in the lamp by means of a member of an electrically insulating material and are connected by means of an ignition mass situated on the member, which lamp can be fired by the short-lasting application of a high voltage.

Photoflash lamps of the combustible type are fired by applying a voltage across the poles of the current conductors, which voltage increases to a high value in a very short time. A breakdown occurs in the ignition mass, followed by the passage of current as a result of which heat is generated in the mass followed by explosive combustion. During the passage of current, the voltage across the poles decreases to a low value.

It has been found in practice that the building up of a high voltage across the poles in a short period of time is not always successful. In the majority of the cases this failure of the ignition mechanism has been found to be not due to a wrong composition of the ignition mass or to structural errors, but it has been found to be due to leakage paths for the electric current in the lamp. It has been found that the supplied voltage can drop across said leakage paths to a value which is insufficient to produce a breakdown in the ignition mass between the poles of the current conductors, followed by ohmic heat generation by the passage of current in the ignition mass.

In the majority of cases these leakage paths are formed if parts of the oxidizing metal in the lamp touch the ignition mass or approach it very closely, which cannot be avoided in the normal process.

The invention is based on the recognition of the fact that the present problems do not occur in a photoflash lamp of the combustible type, when the design of the ignition mass and/or the shape of the body containing said mass is subjected to a number of conditions. The photoflash lamp of the combustible type according to the invention is characterized in that the ignition mass and the member containing said mass comprise a recess which surrounds both the ends of the current conductors and the ignition mass connecting said conductors, and that furthermore means are present for keeping the oxidizable metal at such a distance from the ends of the conductors that the breakdown voltage in the ignition mass between the current conductors is smaller than that between the parts of the current conductors situated outside said mass and also smaller than that between any part of a current conductor and the nearest parts of the oxidizable metal. By providing the photoflash lamp with a recess for the ignition mass in this manner, the possibility is obtained of localizing the ignition mass, of which an accurately prescribed dose is provided in the lamp, around the ends of the current conductors in a manner which can substantially entirely be predicted.

It has been found useful to form the recess as a cavity in the insulating body which widens to the outside. As a result of this design parts of the ignition mass are swung to the metal wool or the like to be ignited in a diverging manner so that a better, oriented firing of the lamp is obtained.

In order to fulfill the condition that the breakdown voltage at least between the conductors in the paste be smaller than that between any part of a conductor and the nearest part of the oxidizable metal, the means for keeping said metal at a distance relative to one of the conductor ends may be formed by the ignition mass itself. Said mass is given such a shape that the shortest distance in the mass between the current conductors is smaller than the distance between any part of a current conductor and that surface of the mass with which the oxidizable mass can contact. Separate spacing means are consequently not necessary in this case, and the metal parts can contact the ignition mass without objection and without undesirable leakage paths being present during the short-lasting application of the high voltage.

Alternatively, if desirable, the ignition mass oriented in the recess in the prescribed manner can be surrounded by an annular member which projects to above the surface of the ignition mass remote from the body and the inside diameter of which is chosen to be small so that penetration of the metal into it is counteracted.

The recess may be formed as a craterlike cup in the body of insulating material and the annular member is formed by the edge of the crater which projects above the ignition mass and then forms part of the insulating member. It may alternatively be formed as a glass tube. In that case a separate tubular member is arranged around the ignition mass.

The ignition mass may be situated on the bead of a bead system. However, it may also be provided in a different place in the photofiash lamp, notably 011 the inner wall of the lamp situated nearest the lamp socket which strongly simplifies particularly the manufacture of very elongate flashlight lamps, in which the length is, for example 10 X the diameter and which are sometimes termed needle lamps.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to a few examples and the accompanying drawings, in which FIG. 1 is a diagrammatic longitudinal cross-sectional view of a photoflash lamp of the prior art.

FIG. 2 is a similar cross-sectional view of a photoflash lamp according to the invention,

FIG. 3 is a longitudinal cross-sectional view of a photoflash lamp according to another embodiment; in this embodiment the ignition mass is arranged in the bottom of the lamp.

FIG. 4 relates to a needlelike photoflash lamp, and

FIG. 5 is a partial view in cross section in an enlarged scale of a recess provided with a quantity of ignition mass.

FIG. 1 shows a photoflash lamp which is provided with a transparent envelope 1 or bulb part. The lamp contains an oxidizable metal, for example, zirconium wool, and is filled with oxygen or another gas for reacting with the metal wool. The ignition mechanism comprises two current conductors 5 and 7, which are sealed in a head 9 and are insulated electrically relative to the metal wool 3 over the parts of the conductors between the bead and the bottom of the envelope. The ends of the current supply wires 5, 7 are interconnected by an ignition mass 11 which consists of a mixture of an oxidizing agent, an oxidizable material and a binder. The mass may furthermore comprise an electrically conductive material and an activator. A suitable ignition mass contains, for example, 34.2 percent by weight of zirconium powder, 25.4 percent by weight of potassium perchlorate, 1.9 percent by weight of red phosphorous, 25.8 percent by weight of semiconductive lanthanum cobaltite (La Sn Co0 and 2.7 percent by weight of nitrocellulose as a binder. By applying a voltage, which increases to a high value in a very short period of time, across the conductors 5 and 7, breakdown occurs in the ignition mass 11, followed by ohmic heat generation due to current passage in the ignition mass. In this case, for example, a piezoelectric voltage source is used.

It has been found that undesirable leakage paths for the electric current in the lamp which give rise to nonfiring of the lamp, can be prevented by providing the ignition mass 11 in a recess 13 of the bead 9, within which the ends of the conductors 5 and 7 end at a suitable distance from each other (See FIG. 2). The ignition mass is provided in said recess in a liquid condition initially and them assumes the shape as shown in FIG. 2. This recess 13 which may be in the form of a groove or surface of a cone is preferably shaped so that the ignition mass, after ignition, provides a stream of combustion products which are thrown in a strongly divergent direction toward the metal W00] 3 to be burnt.

In contrast with the lamps shown in FIGS. 1 and 2, in which a bead or the like is arranged in a higher place of the envelope, the body from insulating material in the lamps shown in FIGS. 3 and 4 is formed by the lamp socket itself. In this case also, the ignition mass is again provided in a cavity which widens towards the metal wool or the like to be burnt, which in FIG. 3

is denoted by 15 and in FIG. 4 is denoted by 17. The lamp shown in FIG. 3 has a more squat shape and the lamp shown in FIG. 4 has a very elongate shape.

In each of the lamps shown in FIGS. 2, 3 and 4 means are present for causing the breakdown voltage in the ignition mass between two current conductors to be smaller than that between one of the conductors and the nearest parts of the oxidizable metal wool. For this purpose, it is sufficient essentially to give the ignition mass such a configuration that the distance between the current conductors is always smaller than the distance b" between one of the conductors and the surface of the ignition mass facing the zirconium wool 3 (FIG. 5). This can often be obtained by suitable shape of the recess in the insulating member itself. So in that case the said means are formed by a layer of ignition mass having a thickness b.

In a number of cases where dimension a between the conductor ends has an established minimum, and where the prescribed quantity of ignition mass would result in a configuration in which the dimension b becomes even smaller than the dimension a, the insulating means may also comprise an annular member which projects to above the ignition mass. This member may be a glass tube which is shown in broken lines in FIGS. 2 and 3 and is denoted by 19 and 21. The inside diameter of this tube is chosen to be so that metal wool 3 cannot contact the ignition mass 1 1.

Instead of a glass tube 19 or 21 the annular member may alternatively be formed as a bulged circumferential edge 23 in the inner wall 23 of the lamp socket which surrounds the recess 17 (see FIG. 4). In this case the recess 17 has a craterlike shape which also keeps the metal wool 3 at a distance from the ignitor mass 1 1.

What is claimed is:

l. A photofiash lamp comprising a. an envelope of light-pervious electrically nonconductive material defining a base part and a bulb part having a top end remote from the base part, the base part defining on its inner surface facing said top end a cavity that diverges outward toward said top end,

b. a mass of oxidizable material and oxidizing gas sealed within the bulb part,

c. two spaced current conductors having one end of each extending through the base part and into said cavity within the interior of the bulb part,

d. an ignition mass situated in said cavity with said current conductor ends embedded in said mass, the ends maintained apart a distance such that the breakdown voltage in the ignition mass is less than between any other parts of the two conductors and less than between any part of a conductor and said oxidizable metal.

2. A lamp according to claim 1 further comprising an annular member of electrically nonconductive material disposed generally surrounding the ignition mass with the open end of the annular member facing said top end, for maintaining said mass from physically contacting the oxidizable metal in the bulb.

3. A lamp according to claim 2 wherein the annular member has a bottom portion adjacent the base part and an upper portion that extends higher above the base than said ignition mass.

4. A lamp according to claim 1 wherein said cavity in the base has circumferential outer edge that defines an upward extending ridge having a diameter less than that of the bulb.

5. A photoflash lamp comprising a. an envelope of light-pervious material defining a base part and a bulb part having a top end remote from the base part,

b. a mass of oxidizable material and oxidizing gas sealed within the bulb part,

c. two current conductors having one end each extending through the base part to a location within the bulb part,

d. an electrically nonconductive bead through which said two ends extend, the bead supporting and maintaining said ends at a fixed distance apart, the bead defining on its upper surface facing said top end of the bulb part cavity that diverges outward toward said top end, e. an ignition mass situated in said cavity and in which said conductor ends are embedded and maintained apart a distance such that the breakdown voltage in said mass is less than between any other parts of the two conductors and less than between any part of a conductor and said oxidizing metal.

6. A lamp according to claim 5 further comprising an annular member of electrically nonconductive material disposed generally surrounding the ignition mass with the open end of the annular member facing said top end, for maintaining said mass from physically contacting the oxidizable metal in the bulb.

7. A lamp according to claim 6 wherein the annular member has a bottom portion adjacent the base part and an upper portion that extends higher above the base than said ignition mass. 

1. A photoflash lamp comprising a. an envelope of light-pervious electrically nonconductive material defining a base part and a bulb part having a top end remote from the base part, the base part defining on its inner surface facing said top end a cavity that diverges outward toward said top end, b. a mass of oxidizable material and oxidizing gas sealed Within the bulb part, c. two spaced current conductors having one end of each extending through the base part and into said cavity within the interior of the bulb part, d. an ignition mass situated in said cavity with said current conductor ends embedded in said mass, the ends maintained apart a distance such that the breakdown voltage in the ignition mass is less than between any other parts of the two conductors and less than between any part of a conductor and said oxidizable metal.
 2. A lamp according to claim 1 further comprising an annular member of electrically nonconductive material disposed generally surrounding the ignition mass with the open end of the annular member facing said top end, for maintaining said mass from physically contacting the oxidizable metal in the bulb.
 3. A lamp according to claim 2 wherein the annular member has a bottom portion adjacent the base part and an upper portion that extends higher above the base than said ignition mass.
 4. A lamp according to claim 1 wherein said cavity in the base has circumferential outer edge that defines an upward extending ridge having a diameter less than that of the bulb.
 5. A photoflash lamp comprising a. an envelope of light-pervious material defining a base part and a bulb part having a top end remote from the base part, b. a mass of oxidizable material and oxidizing gas sealed within the bulb part, c. two current conductors having one end each extending through the base part to a location within the bulb part, d. an electrically nonconductive bead through which said two ends extend, the bead supporting and maintaining said ends at a fixed distance apart, the bead defining on its upper surface facing said top end of the bulb part cavity that diverges outward toward said top end, e. an ignition mass situated in said cavity and in which said conductor ends are embedded and maintained apart a distance such that the breakdown voltage in said mass is less than between any other parts of the two conductors and less than between any part of a conductor and said oxidizing metal.
 6. A lamp according to claim 5 further comprising an annular member of electrically nonconductive material disposed generally surrounding the ignition mass with the open end of the annular member facing said top end, for maintaining said mass from physically contacting the oxidizable metal in the bulb.
 7. A lamp according to claim 6 wherein the annular member has a bottom portion adjacent the base part and an upper portion that extends higher above the base than said ignition mass. 